[emulator] Place call arguments using the emulated function's calling convention

SetArgument always used the platform's default calling convention, contradicting
the documented behavior of using the function's own convention. Derive the
calling convention from the function being emulated (via its LLIL function),
falling back to the platform default only when the function has none. Also note
the address-size-as-stack-slot-size assumption for exotic ABIs.

Addresses emesare review comments on PR #8314.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: xusheng6

plugins/emulator/core/llilemulator.cpp

@@ -72,11 +72,19 @@ void LLILEmulator::SetArgument(size_t index, const intx::uint512& value)
 	if (!m_view)
 		return;
 
-	Ref<Platform> platform = m_view->GetDefaultPlatform();
-	if (!platform)
-		return;
-
-	Ref<CallingConvention> cc = platform->GetDefaultCallingConvention();
+	// Place arguments using the calling convention of the function being emulated, falling
+	// back to the platform default only when the function has none.
+	Ref<CallingConvention> cc;
+	if (m_il)
+	{
+		if (Ref<Function> func = m_il->GetFunction())
+			cc = func->GetCallingConvention().GetValue();
+	}
+	if (!cc)
+	{
+		if (Ref<Platform> platform = m_view->GetDefaultPlatform())
+			cc = platform->GetDefaultCallingConvention();
+	}
 	if (!cc)
 		return;
 
@@ -87,7 +95,9 @@ void LLILEmulator::SetArgument(size_t index, const intx::uint512& value)
 		return;
 	}
 
-	// Stack argument
+	// Stack argument. Note: the stack slot size is taken to be the address size, which holds
+	// for the common ABIs but not exotic ones like the x86-64 x32 ABI (4-byte address size,
+	// 8-byte stack slots).
 	size_t addrSize = m_arch->GetAddressSize();
 	uint32_t sp = m_arch->GetStackPointerRegister();
 	uint64_t spVal = static_cast<uint64_t>(GetRegister(sp));

plugins/emulator/core/llilemulator.h

@@ -160,7 +160,8 @@ namespace BinaryNinjaEmulator
 		bool SetEntryPoint(uint64_t addr);
 		void SetEntryPoint(BinaryNinja::LowLevelILFunction* il, size_t instrIndex);
 
-		// Argument setup (uses default calling convention)
+		// Argument setup (uses the emulated function's calling convention, falling back to
+		// the platform default)
 		void SetArgument(size_t index, const intx::uint512& value);
 		void SetArguments(const std::vector<uint64_t>& values);